RFID interference with Touchpad

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
lock attach
Attachments are accessible only for community members.
Anonymous
Not applicable

We are using TRF7970 for RFID reader (13.56Mhz).

Touch pads, Proxy and RFID antenna on single PCB. (Please Refer Attached Image)

1. We are using 12 button keypad and button '8' used for proxy sensor as well as button.

2. Configuration by Ezclick tool. (Configuration detail in attachment)

3. It works fine when RFID reader is disabled but when we enabled the RFID reader to detect the card we are getting false interrupt of button pressed from cypress.

Please verify the configuration detail and let me know if I missed any thing else.

I don't know why we are getting false interrupt of button pressed when we enabled RFID reader.

On more observation, when we enabled the RFID after getting proxy event RFID reader not able to read the card as it works fine before. I don't understand why they are disturb each other.

0 Likes
1 Solution
RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

Hi Nirav,

RFID frequency is 13.56MHz. It is close with scanning frequency of CapSense.

One suggestion is, using time-sharing method, RFID work/CapSense stop,  then RFID stop/CapSense work, then RFID work/CapSense stop.....

In addition, you can try increase the series resistor(2.2k, 4.7k) on sensor trace, and add a 10pF filter between the series resistor and MBR3. That may help to reduce the noise from RFID.

Thanks,

Ryan

View solution in original post

0 Likes
4 Replies
RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

Hi Nirav,

RFID frequency is 13.56MHz. It is close with scanning frequency of CapSense.

One suggestion is, using time-sharing method, RFID work/CapSense stop,  then RFID stop/CapSense work, then RFID work/CapSense stop.....

In addition, you can try increase the series resistor(2.2k, 4.7k) on sensor trace, and add a 10pF filter between the series resistor and MBR3. That may help to reduce the noise from RFID.

Thanks,

Ryan

0 Likes
Anonymous
Not applicable

Hi Ryan,

Thanks for you response.

We are using only 560E resistor in current hardware.

As you suggest capacitor(C1_10pF) in series right?

pastedImage_0.png

Thanks,

Nirav Patel

0 Likes
RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

Hi Nirav,

Sorry for the unclear describing in my previous response.

I mean..add a capacitor shorted to ground, between the serial res and the chip for each sensor.

Beside, how about using time-sharing method?

Thanks,

Ryan

Anonymous
Not applicable

Thanks!!! Ryan,

Let me check from my side.

If we need more help than let you know.

Thanks,

Nirav Patel

0 Likes